1. Technical Field
This invention relates to suspensions for disk drives, and more particularly to suspensions useful in suspension-slider combinations. The invention suspensions are in comparison with previously known suspensions insensitive to shock. The suspensions have a lift-off acceleration characteristic of the suspension which is greatly increased over past suspensions, enabling improved shock performance and reduced likelihood of damage from shock and vibration events experienced by the disk drive. The invention suspension has especial utility with 30%-sized, or pico, sliders.
2. Related Art
Pico sliders having very little mass, and thus low inertia, tend readily to lift from a rest position on the disk surface during shock or vibration events in the disk drive. The preload imposed by the suspension in reaction to the movement of the slider forces the slider back against the disk possibly damaging the disk and/or the slider. The possibility of damage is particularly acute when the slider is carried at an angular, that is other than a flat, orientation to the disk at the instant of re-contact with the disk. An angular orientation of the slider may be encountered with presently known suspensions as a result of undue 2nd mode bending of the suspension.
A present challenge in the design of disk drive suspensions is increasing its ability to withstand high shock from the drive and at the same time not to damage the disk surface. The suspension being a cantilever type spring, the lift-off of the suspension depends on mass of the suspension and mass center distance from the rotating axis.
In the design of the present invention there is an extended mounting plate but the load beam length is kept to a total length of about 18 mm. The load beam is laminated by welding a part of the flexure thereto to increase stiffness. The mass center is moved closer to the slider. Hence, the moment developed due to the separation of the mass center and slider is smaller. The force propagated due to this moment through the load beam is smaller in value. This small value creates less traveling force and makes the vibration amplitude less.
Features of the present load beam include:
1. Mass center (e.g.) is close to the slider and the moment developed from two opposite forces (one from reaction force from slider and the other from inertial force) is small.
2. Small traveling force creates less magnitude of excitation force in the beam and less amplitude of vibration.
3. Laminated load beam and flexure welded together in the rail area, combined with a small travelling force tend to excite 1st bending mode of the beam, not 2nd bending mode. By exciting the lower, 1st bending mode, the vibration from the flexure bend-up is decoupled from torsion modes of vibration.
4. Design bias toward the 1st bending mode causes the slider to hit the disk flat in comparison to 2nd bending mode bend-up of the beam.
5. As the pico slider is very small in size, shortening the load beam flying mass from 0.61 inch to 0.51 inch by having extended mount plate, results in 16% small load beam. The shorter load beam is more stable and its vibration amplitude gain is relatively small.
6. The wide body of the load beam makes the beam laterally stiff and hence improves sway and torsion modes.
7. The invention load beam longer vertical spring area allows more room to form optimized spring (to improve modes of vibrations and lower de-gramming) since stress due to bending is distributed over larger area.
In accordance with the invention, there is provided a substantially shock-insensitive disk drive suspension comprising a longitudinally extended load beam, a mounting plate for mounting the load beam to an actuator, the load beam having a base portion affixed to the mounting plate, a front portion of a predetermined width to which a flexure is attached, and a spring portion between the base portion and the front portion, the base portion being extended and the front portion shortened by the mounting plate having an extension at least 50% more in the load beam longitudinal direction as in the transverse direction, the flexure having substantially the predetermined width of the front portion and being laminated thereto, the load beam and the flexure having their respective centers of gravity spaced a distance 1, the distance 1 having a value minimizing the reaction moment Mr of the load beam when the load beam receives a shock force to thereby reduce the 2nd bending moment excitation of the load beam.
In this and like embodiments, typically, the load beam front portion has side rails and comprises between 30 and 40% of the total length of the load beam; the load beam spring portion comprises between 20 and 25% of the total length of the load beam; the load beam base portion mounting plate has a length between 30 and 40% of the total length of the load beam, and the suspension has the following properties:
A 1st torsion frequency of about 3.6 Khz
A 2nd torsion frequency of about 9.6 Khz
A Sway or lateral bending frequency of about 12.3 Khz
A Lift-off acceleration above about 110 xe2x80x98gxe2x80x99/gm